Materials
Everything here was chosen to be buyable in an ordinary Mexican hardware store, aquarium shop or garden centre. No laboratory equipment is required.
Column
| Item | Quantity | Where |
|---|---|---|
| Transparent acrylic tube, 3 in bore | 700 mm | acrylic supplier |
| Volcanic scoria (lava rock), raw | 3 kg | garden centre |
| Granular activated carbon | 500 g | aquarium shop |
| Aquarium gravel | 1 kg | aquarium shop |
| Transparent hose, ½ in | 1 m | hardware store |
| Plastic stopcock, ½ in | 1 | hardware store |
| Plastic insect mesh | 30 × 30 cm | hardware store |
| Transparent silicone | 1 tube | hardware store |
Transparency is not cosmetic. The layers have to be visible for the column to explain itself in a photograph, which is most of what the build is for.
Measurement
| Item | Quantity | Note |
|---|---|---|
| Identical glass jars | 6 | straight-sided, clear, no embossing |
| Syringes, no needle | 3 × 20 ml | for the dilution series |
| Kitchen measuring jug | 1 L | replaces a graduated cylinder |
| Blue food colouring | 1 | strong, not pale |
| Neutral liquid soap | 1 | surfactant load |
| White card | 80 × 80 mm | exposure reference |
| Printed checker target | 100 × 100 mm | contrast target |
| Constant lamp | 1 | any fixed light source |
Why the jars must be identical
Every sample is photographed through glass. Different thickness or curvature changes what the camera sees, and the series stops comparing anything. Six matching jam jars work as well as six bought ones.
Blue is not an arbitrary choice. The methylene blue number is the standard industrial test for the adsorption capacity of activated carbon, so a blue tracer mirrors the real assay — and blue reads as dark grey once the photograph is converted, which is what the contrast measurement needs. Yellow reads almost white and is nearly invisible to the method.
Deliberately not required
| Not needed | Instead |
|---|---|
| Laboratory sieve stack | Insect mesh as a single cut, aperture measured and reported |
| Precision balance | Media placed by depth; volumes recorded rather than masses |
| Geotextile | Discs cut from the same insect mesh |
| Graduated cylinder | Kitchen measuring jug |
| Clamps and stand | A cardboard box with a hole cut in the top |
| Nephelometer | Photographs and the analysis code |
The box is worth a word. The column passes through a hole in the lid, the outlet and collecting jar sit hidden inside, and on camera the result reads as a column standing on a plinth rather than a tube strapped to a chair.
Not handled
No perchlorates
Perchlorate salts are strong oxidisers. They are not used, not bought, and not required. Stage 1 is supported by published work; what the bench demonstrates is filtration and adsorption, measured with synthetic greywater mixed to a written recipe.